<chapter id="examples">
- <!-- $Id: examples.xml,v 1.5 2002-09-19 19:51:48 adam Exp $ -->
<title>Example Configurations</title>
- <sect1>
+ <sect1 id="examples-overview">
<title>Overview</title>
<para>
- <literal>zebraidx</literal> and <literal>zebrasrv</literal> are both
+ <command>zebraidx</command> and
+ <command>zebrasrv</command> are both
driven by a master configuration file, which may refer to other
subsidiary configuration files. By default, they try to use
<filename>zebra.cfg</filename> in the working directory as the
- master file; but this can be changed using the <literal>-t</literal>
+ master file; but this can be changed using the <literal>-c</literal>
option to specify an alternative master configuration file.
</para>
<para>
- The master configuration file tells Zebra:
+ The master configuration file tells &zebra;:
<itemizedlist>
<listitem>
<para>
- Where to find the default indexing rules (### default.idx)
+ Where to find subsidiary configuration files, including both
+ those that are named explicitly and a few ``magic'' files such
+ as <literal>default.idx</literal>,
+ which specifies the default indexing rules.
</para>
</listitem>
<listitem>
<para>
- ### Something to do with explain.abs?!
+ What record schemas to support. (Subsidiary files specify how
+ to index the contents of records in those schemas, and what
+ format to use when presenting records in those schemas to client
+ software.)
</para>
</listitem>
<listitem>
<para>
- ### Where to find other configuration files, e.g. searches using
- BIB-1 attributes require a bib1.att configuration file (even if
- the access point is actually an XPath expression). These are
- searched for in the working directory unless otherwise
- specified.
+ What attribute sets to recognise in searches. (Subsidiary files
+ specify how to interpret the attributes in terms
+ of the indexes that are created on the records.)
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ Policy details such as what type of input format to expect when
+ adding new records, what low-level indexing algorithm to use,
+ how to identify potential duplicate records, etc.
</para>
</listitem>
</itemizedlist>
</para>
+ <para>
+ Now let's see what goes in the <literal>zebra.cfg</literal> file
+ for some example configurations.
+ </para>
</sect1>
<sect1 id="example1">
- <title>Example 1: Minimal Configuration</title>
+ <title>Example 1: &acro.xml; Indexing And Searching</title>
<para>
- This example shows how Zebra can be used with absolutely minimal
- configuration to index a body of XML documents, and search them
- using XPath expressions to specify access points.
+ This example shows how &zebra; can be used with absolutely minimal
+ configuration to index a body of
+ <ulink url="&url.xml;">&acro.xml;</ulink>
+ documents, and search them using
+ <ulink url="&url.xpath;">XPath</ulink>
+ expressions to specify access points.
</para>
<para>
- Go to the <literal>zebra/examples/dinosauricon</literal> directory.
- There you will find a <literal>records</literal> subdirectory,
- which contains some raw XML data to be added to the database: in
- this case, two files, <literal>genera.xml</literal> and
- <literal>taxa.xml</literal>, which contain information about all
- the known dinosaur genera as of August 2002.
+ Go to the <literal>examples/zthes</literal> subdirectory
+ of the distribution archive.
+ There you will find a <literal>Makefile</literal> that will
+ populate the <literal>records</literal> subdirectory with a file of
+ <ulink url="http://zthes.z3950.org/">Zthes</ulink>
+ records representing a taxonomic hierarchy of dinosaurs. (The
+ records are generated from the family tree in the file
+ <literal>dino.tree</literal>.)
+ Type <literal>make records/dino.xml</literal>
+ to make the &acro.xml; data file.
+ (Or you could just type <literal>make dino</literal> to build the &acro.xml;
+ data file, create the database and populate it with the taxonomic
+ records all in one shot - but then you wouldn't learn anything,
+ would you? :-)
</para>
<para>
- Now we need to create the Zebra database, which we do with the
- Zebra indexer, <literal>zebraidx</literal>. This program's
- behaviour is driven by a configuration life, generally called
- <literal>zebra.cfg</literal>, although this can be changed with the
- <literal>-c</literal> option. For our purposes, we don't need any
- special behaviour - we can use the defaults - so an empty
- configuration will do just fine. We can either create an empty
- <literal>zebra.cfg</literal> or specify the name of an existing
- empty file using, for example, <literal>-c /dev/null</literal>.
- </para>
- <para>
- In this case, we'll use an empty <literal>zebra.cfg</literal> so
- we can add more configuration to it later.
+ Now we need to create a &zebra; database to hold and index the &acro.xml;
+ records. We do this with the
+ &zebra; indexer, <command>zebraidx</command>, which is
+ driven by the <literal>zebra.cfg</literal> configuration file.
+ For our purposes, we don't need any
+ special behaviour - we can use the defaults - so we can start with a
+ minimal file that just tells <command>zebraidx</command> where to
+ find the default indexing rules, and how to parse the records:
+ <screen>
+ profilePath: .:../../tab
+ recordType: grs.sgml
+ </screen>
</para>
<para>
- That's all you need for a minimal Zebra configuration. Now you can
- roll the XML records into the database and build the indexes:
+ That's all you need for a minimal &zebra; configuration. Now you can
+ roll the &acro.xml; records into the database and build the indexes:
<screen>
- zebraidx -t grs.sgml update records
+ zebraidx update records
</screen>
- (### What does "grs.sgml" actually mean?)
</para>
<para>
Now start the server. Like the indexer, its behaviour is
- controlled by a configuration file, generally
- <literal>zebra.cfg</literal>; and like the indexer, it works just
- fine with an empty configuration.
+ controlled by the
+ <literal>zebra.cfg</literal> file; and like the indexer, it works
+ just fine with this minimal configuration.
<screen>
zebrasrv
</screen>
By default, the server listens on IP port number 9999, although
- this can easily be changed.
+ this can easily be changed - see
+ <xref linkend="zebrasrv"/>.
</para>
<para>
- Now you can use the Z39.50 client program of your choice to execute
- XPath-based boolean queries and fetch the XML records that satisfy
+ Now you can use the &acro.z3950; client program of your choice to execute
+ XPath-based boolean queries and fetch the &acro.xml; records that satisfy
them:
<screen>
- Z> open tcp:@:9999
- Connecting...Ok.
- Z> find @attr 1=/GENUS/MEANING @or vertebra jaw
- Number of hits: 1
- Z> format xml
- Z> show 1
- Z> show 1
- <GENUS name="Hudiesaurus" type="with" xmlns:idzebra="http://www.indexdata.dk/zebra/">
- <MEANING>
- butterfly <LOW>vertebra</LOW> lizard
- </MEANING>
- <LENGTH value="30"></LENGTH>
- <PLACE name="China"></PLACE>
- <REMAINS content="4 teeth, forelimb, first dorsal vertebra"></REMAINS>
- <SPECIES name="sinojapanorum" status="nudum">
- <AUTHOR name="Dong" year="1997"></AUTHOR>
- <MEANING>
- Chinese-Japanese
- </MEANING>
- </SPECIES>
- <idzebra:size>359</idzebra:size><idzebra:localnumber>447</idzebra:localnumber><idzebra:filename>records/genera.xml</idzebra:filename></GENUS>
+ $ yaz-client @:9999
+ Connecting...Ok.
+ Z> find @attr 1=/Zthes/termName Sauroposeidon
+ Number of hits: 1
+ Z> format xml
+ Z> show 1
+ <Zthes>
+ <termId>22</termId>
+ <termName>Sauroposeidon</termName>
+ <termType>PT</termType>
+ <termNote>The tallest known dinosaur (18m)</termNote>
+ <relation>
+ <relationType>BT</relationType>
+ <termId>21</termId>
+ <termName>Brachiosauridae</termName>
+ <termType>PT</termType>
+ </relation>
+
+ <idzebra xmlns="http://www.indexdata.dk/zebra/">
+ <size>300</size>
+ <localnumber>23</localnumber>
+ <filename>records/dino.xml</filename>
+ </idzebra>
+ </Zthes>
</screen>
</para>
<para>
- Now wasn't that easy?
+ Now wasn't that nice and easy?
</para>
</sect1>
+
<sect1 id="example2">
- <title>Example 2: Adding Some Configuration</title>
+ <title>Example 2: Supporting Interoperable Searches</title>
<para>
- You may have noticed as <literal>zebraidx</literal> was building
- the database that it issued several warnings, which we ignored at
- the time:
- <screen>
-zebraidx -t grs.sgml update records
-02:12:32-30/08: zebraidx(18151) [warn] default.idx [No such file or directory]
-02:12:32-30/08: zebraidx(18151) [warn] Couldn't open explain.abs [No such file or directory]
-02:12:32-30/08: zebraidx(18151) [warn] records/genera.xml:0 Couldn't open GENUS.abs [No such file or directory]
-02:12:32-30/08: zebraidx(18151) [warn] records/genera.xml:0 Unknown register type: 0
-02:12:32-30/08: zebraidx(18151) [warn] records/genera.xml:0 Unknown register type: w
-02:12:35-30/08: zebraidx(18151) [warn] records/taxa.xml:0 Couldn't open TAXON.abs [No such file or directory]
- </screen>
- And the server issued several more as the client connected to it,
- then searched for and retrieved a record:
- <screen>
-02:17:10-30/08: zebrasrv(18165) [warn] default.idx [No such file or directory]
-02:17:10-30/08: zebrasrv(18165) [warn] Couldn't open explain.abs [No such file or directory]
-02:17:57-30/08: zebrasrv(18165) [warn] Unknown register type: w
-02:18:42-30/08: zebrasrv(18165) [warn] Couldn't open GENUS.abs [No such file or directory]
- </screen>
+ The problem with the previous example is that you need to know the
+ structure of the documents in order to find them. For example,
+ when we wanted to find the record for the taxon
+ <foreignphrase role="taxon">Sauroposeidon</foreignphrase>,
+ we had to formulate a complex XPath
+ <literal>/Zthes/termName</literal>
+ which embodies the knowledge that taxon names are specified in a
+ <literal><termName></literal> element inside the top-level
+ <literal><Zthes></literal> element.
+ </para>
+ <para>
+ This is bad not just because it requires a lot of typing, but more
+ significantly because it ties searching semantics to the physical
+ structure of the searched records. You can't use the same search
+ specification to search two databases if their internal
+ representations are different. Consider a different taxonomy
+ database in which the records have taxon names specified
+ inside a <literal><name></literal> element nested within a
+ <literal><identification></literal> element
+ inside a top-level <literal><taxon></literal> element: then
+ you'd need to search for them using
+ <literal>1=/taxon/identification/name</literal>
+ </para>
+ <para>
+ How, then, can we build broadcasting Information Retrieval
+ applications that look for records in many different databases?
+ The &acro.z3950; protocol offers a powerful and general solution to this:
+ abstract ``access points''. In the &acro.z3950; model, an access point
+ is simply a point at which searches can be directed. Nothing is
+ said about implementation: in a given database, an access point
+ might be implemented as an index, a path into physical records, an
+ algorithm for interrogating relational tables or whatever works.
+ The only important thing is that the semantics of an access
+ point is fixed and well defined.
+ </para>
+ <para>
+ For convenience, access points are gathered into <firstterm>attribute
+ sets</firstterm>. For example, the &acro.bib1; attribute set is supposed to
+ contain bibliographic access points such as author, title, subject
+ and ISBN; the GEO attribute set contains access points pertaining
+ to geospatial information (bounding coordinates, stratum, latitude
+ resolution, etc.); the CIMI
+ attribute set contains access points to do with museum collections
+ (provenance, inscriptions, etc.)
+ </para>
+ <para>
+ In practice, the &acro.bib1; attribute set has tended to be a dumping
+ ground for all sorts of access points, so that, for example, it
+ includes some geospatial access points as well as strictly
+ bibliographic ones. Nevertheless, this model
+ allows a layer of abstraction over the physical representation of
+ records in databases.
</para>
+ <para>
+ In the &acro.bib1; attribute set, a taxon name is probably best
+ interpreted as a title - that is, a phrase that identifies the item
+ in question. &acro.bib1; represents title searches by
+ access point 4. (See
+ <ulink url="&url.z39.50.bib1.semantics;">The &acro.bib1; Attribute
+ Set Semantics</ulink>)
+ So we need to configure our dinosaur database so that searches for
+ &acro.bib1; access point 4 look in the
+ <literal><termName></literal> element,
+ inside the top-level
+ <literal><Zthes></literal> element.
+ </para>
+ <para>
+ This is a two-step process. First, we need to tell &zebra; that we
+ want to support the &acro.bib1; attribute set. Then we need to tell it
+ which elements of its record pertain to access point 4.
+ </para>
+ <para>
+ We need to create an <link linkend="abs-file">Abstract Syntax
+ file</link> named after the document element of the records we're
+ working with, plus a <literal>.abs</literal> suffix - in this case,
+ <literal>Zthes.abs</literal> - as follows:
+ </para>
+ <programlistingco>
+ <areaspec>
+ <area id="attset.zthes" coords="2"/>
+ <area id="attset.attset" coords="3"/>
+ <area id="termId" coords="7"/>
+ <area id="termName" coords="8"/>
+ </areaspec>
+ <programlisting>
+attset zthes.att
+attset bib1.att
+xpath enable
+systag sysno none
+
+xelm /Zthes/termId termId:w
+xelm /Zthes/termName termName:w,title:w
+xelm /Zthes/termQualifier termQualifier:w
+xelm /Zthes/termType termType:w
+xelm /Zthes/termLanguage termLanguage:w
+xelm /Zthes/termNote termNote:w
+xelm /Zthes/termCreatedDate termCreatedDate:w
+xelm /Zthes/termCreatedBy termCreatedBy:w
+xelm /Zthes/termModifiedDate termModifiedDate:w
+xelm /Zthes/termModifiedBy termModifiedBy:w
+ </programlisting>
+ <calloutlist>
+ <callout arearefs="attset.zthes">
+ <para>
+ Declare Thesaurus attribute set. See <filename>zthes.att</filename>.
+ </para>
+ </callout>
+ <callout arearefs="attset.attset">
+ <para>
+ Declare &acro.bib1; attribute set. See <filename>bib1.att</filename> in
+ &zebra;'s <filename>tab</filename> directory.
+ </para>
+ </callout>
+ <callout arearefs="termId">
+ <para>
+ This xelm directive selects contents of nodes by XPath expression
+ <literal>/Zthes/termId</literal>. The contents (CDATA) will be
+ word searchable by Zthes attribute termId (value 1001).
+ </para>
+ </callout>
+ <callout arearefs="termName">
+ <para>
+ Make <literal>termName</literal> word searchable by both
+ Zthes attribute termName (1002) and &acro.bib1; attribute title (4).
+ </para>
+ </callout>
+ </calloutlist>
+ </programlistingco>
+ <para>
+ After re-indexing, we can search the database using &acro.bib1;
+ attribute, title, as follows:
+ <screen>
+Z> form xml
+Z> f @attr 1=4 Eoraptor
+Sent searchRequest.
+Received SearchResponse.
+Search was a success.
+Number of hits: 1, setno 1
+SearchResult-1: Eoraptor(1)
+records returned: 0
+Elapsed: 0.106896
+Z> s
+Sent presentRequest (1+1).
+Records: 1
+[Default]Record type: &acro.xml;
+<Zthes>
+ <termId>2</termId>
+ <termName>Eoraptor</termName>
+ <termType>PT</termType>
+ <termNote>The most basal known dinosaur</termNote>
+ ...
+ </screen>
+ </para>
</sect1>
</chapter>
-<!--
-
- <listitem>
- <para>
- The master configuration file, <literal>zebra.cfg</literal>,
- which is as short and simple as it can be:
- <screen>
- # $Header: /home/cvsroot/idis/doc/examples.xml,v 1.5 2002-09-19 19:51:48 adam Exp $
- # Bare-bones master configuration file for Zebra
- profilePath: .:../../tab:../../../yaz/tab
- </screen>
- Apart from the comments, which are ignored, all this specifies is
- that the server should recognise the attribute set described in
- the file called
- <literal>bib1.att</literal>.
- ### What is an attribute set?
- </para>
- </listitem>
-
- <listitem>
- <para>
- The BIB-1 attribute set configuration file,
- <literal>bib1.att</literal>, which is also as short as possible:
- <screen>
- # $Header: /home/cvsroot/idis/doc/examples.xml,v 1.5 2002-09-19 19:51:48 adam Exp $
- # Bare-bones BIB-1 attribute set file for Zebra
- reference Bib-1
- </screen>
- Apart from the comments, all this specifies is that reference of
- the attribute set described by this file is
- <literal>Bib-1</literal>, a name recognised by the system as
- referring to a well-known opaque identifier that is transmitted
- by clients as part of their searches.
- ### Yeuch! Surely we can say that better!
- </para>
- <para>
- ### Can't we somehow say this trivial thing in the main
- configuration file?
- </para>
- </listitem>
--->
<!--
The simplest hello-world example could go like this:
elm (2,21) subject subject
-->
+<!--
+How to include images:
+
+ <mediaobject>
+ <imageobject>
+ <imagedata fileref="system.eps" format="eps">
+ </imageobject>
+ <imageobject>
+ <imagedata fileref="system.gif" format="gif">
+ </imageobject>
+ <textobject>
+ <phrase>The Multi-Lingual Search System Architecture</phrase>
+ </textobject>
+ <caption>
+ <para>
+ <emphasis role="strong">
+ The Multi-Lingual Search System Architecture.
+ </emphasis>
+ <para>
+ Network connections across local area networks are
+ represented by straight lines, and those over the
+ internet by jagged lines.
+ </caption>
+ </mediaobject>
+
+Where the three <*object> thingies inside the top-level <mediaobject>
+are decreasingly preferred version to include depending on what the
+rendering engine can handle. I generated the EPS version of the image
+by exporting a line-drawing done in TGIF, then converted that to the
+GIF using a shell-script called "epstogif" which used an appallingly
+baroque sequence of conversions, which I would prefer not to pollute
+the &zebra; build environment with:
+
+ #!/bin/sh
+
+ # Yes, what follows is stupidly convoluted, but I can't find a
+ # more straightforward path from the EPS generated by tgif's
+ # "Print" command into a browser-friendly format.
+
+ file=`echo "$1" | sed 's/\.eps//'`
+ ps2pdf "$1" "$file".pdf
+ pdftopbm "$file".pdf "$file"
+ pnmscale 0.50 < "$file"-000001.pbm | pnmcrop | ppmtogif
+ rm -f "$file".pdf "$file"-000001.pbm
+
+-->
+
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